In a known boring bar of this kind, the cutting body of hard metal is brazed onto a tapered extension of the shank of the recessing tool. The shank may either be of cylindrical form and then be arranged in a cylindrical receiving bore, or, and this is more frequently the case, it has a square cross-section and is arranged in a receiving bore of square cross-section. The square cross-section is chosen in order to avoid turning movements of the recessing tool in the receiving bore. A retaining screw acting directly on the shank serves to hold the recessing tool in the receiving bore. Adjusting devices of any kind for adjusting the recessing tool in the radial direction are generally not provided on boring bars. The recessing tools with a brazed-on cutting body which are usually employed with boring bars have the disadvantage that they lose precision of profile as a result of the regrinding that is frequently required. Because of this, not only is it necessary to fall back on keeping a large stock, but regrinding equipment also has to be procured and maintained. Since the recessing tools employed with boring bars generally have a square shank, it is also not possible for the user of these recessing tools to make a toolholder or boring bar for himself. Moreover, two recessing tools cannot be arranged closely side by side in the known construction, since for reasons of stability their shanks must not fall below a certain cross-section. The arrangement of two recessing tools close beside one another is necessary, however, when it is desired to make two grooves simultaneously in a bore, for example two Seeger ring recesses in front and at the back of a ball bearing or some other machine element. The known method of mounting and securing recessing tools in boring bars and other toolholders is also not possible for up-to-date production on machining centres and numerically controlled machines, or on special machines and multi-station machines, since such machines postulate tools which can be produced as simply and rapidly as possible, are adjustable or settable and resettable and can be combined easily with other tools.
The problem underlying the invention is to provide a toolholder for recessing operations, in particular a boring bar of the kind mentioned at the beginning, wherein the cutting body is held in the boring bar so that it is exchangeable and radially adjustable and wherein, moreover, a plurality of cutting bodies can be arranged closely side by side, the parts for receiving and holding the cutting bodies having structural dimensions which are as small as possible and the receiving bore in the toolholder or boring bar being simple to produce.
According to the invention, this is achieved in that the receiving bore is formed as a blind bore that in the blind bore there is arranged a tool support with a substantially semi-cylindrical shank having in its plane supporting surface facing the retaining screw at least one groove extending parallel to its axis for receiving an exchangeable cutting body slidably mounted in the groove, that a clamping jaw for each cutting body is provided in the other remaining half of the blind bore and, under the action of the retaining screw, is supported by its front, outer, end on the top of the cutting body and by its rear end on the supporting surface of the tool support, and that the clamping jaw has at its front end a shoulder supporting the cutting body in the direction of sliding and is provided with a setscrew extending parallel to the groove, the rear end of the setscrew being supported on the base of the blind bore and its front end being accessible through a bore opening out in the outer end face of the clamping jaw.
The novel nature of the arrangement and fixing of recessing cutting bodies requires only a comparatively small space, so that it is particularly suitable for boring bars. For example, to accommodate two cutting bodies, which may be arranged closely side by side at any desired distance apart, only one blind bore with a diameter of 16 mm and a depth of about 30 mm is necessary. The blind bore and the threads for receiving the retaining screws can be produced with simple means, so that the user of such toolholders and boring bars can even produce these himself. Since the cutting body is exchangeable, regrinding operations and the inaccuracies associated therewith are eliminated. Moreover, the cutting body or bodies is or are conveniently and accurately adjustable in the longitudinal direction by means of externally accessible setscrews. This is an advantage in particular when there is to be provided on one toolholder a plurality of cutting bodies whose cutting edges must be positioned precisely with respect to the toolholder. In the supporting surface of the tool support there may be provided one, two or even three grooves with different distances between them and of different widths, in which the appropriate cutting bodies are then arranged. In this way, the toolholder can be adapted to the most diverse machining tasks. It is envisaged that the tool support, the cutting bodies and the clamping jaws, the production of which requires a certain precision, will be made in a tool factory specialised for the purpose, while the toolholder or boring bar itself can be made by the user of the tools. Of course, it is also possible for the toolholder or boring bar to be made by the tool factory together with the other parts.